The prior art discloses a variety of conventional extended reach right-angle machining systems, some of which have a limited reach (e.g. about one meter or forty inches) and a large external size (e.g. about thirteen centimeters or five inches) for certain applications in removing material internally from a member. Certain prior systems with an extended reach spindle arm made from a single piece shaft and housing have problems due to resonance and vibration, and due to various disadvantages in methods for making such systems.
Certain conventional right-angled machining head designs are suitable for a variety of applications, but some systems with a reach of over forty inches perform ineffectively. The shaft size of some prior systems results in a relatively long shaft with bearing supports at either end which has a low critical speed. Bending or sag in the shaft system can produce whipping of the shaft at even low speeds. One piece shaft arrangements can have a small cross-sectional area due to housing size and bearing location diameter, which can limit torque and reduce torsional stiffness. Often balancing a relatively long one-piece shaft for operation at high rpm's can be impractical. Since torsional stiffness is required to prevent fatigue, and if cyclic vibration is transmitted to a spindle head, oscillations in the spindle of certain prior systems reduces tool bit life and spindle head life.
Manufacturing a shaft in one piece can create significant production problems with machining accuracy (e.g. regarding concentricity, circularity, straightness, and parallel locating faces). Differential thermal expansion of a relatively long shaft and housing can cause excessive loads on bearings or promote whipping during operation. With certain relatively long shafts, there are difficulties in providing auxiliary services to a cutting head on the shaft, e.g. providing cooling/lubricating oil for a gearbox; providing coolant for machining tool; and swarf removal.
The prior art discloses a variety of systems for material removal, e.g., but not limited to, as disclosed in and referred to in U.S. Pat. Nos. 2,372,913; 3,037,429; 3,568,568; 5,025,548; 5,240,360; 5,664,917; and German Patent No. DT 2,120,133—all incorporated fully by reference herein for all purposes.
The prior art discloses a wide variety of downhole motors, mud motors, power sections, artificial lift progressive cavity pumps, industrial progressive cavity pumps, parts thereof, and methods for making them, including, but not limited to, those in U.S. Pat. Nos. 3,084,631; 3,499,830; 3,547,798; 3,553,095; 3,616,343; 3,769,194; 3,896,012; 4,104,009; 4,250,371; 4,376,020; 4,391,547; 4,475,996; 4,772,246; 4,909,337; 5,417,281; 5,611,397; 5,759,019; 6,019,583; 6,183,226; 6,230,823; 6,568,076; 6,644,358; 6,905,319; and in U.S. Patent Application Nos. 20050079083 published Apr. 14, 2005; and 20030089621 published May 15, 2003—all said patents and applications incorporated herein fully by reference for all purposes.
There is a need, recognized by the present inventors, for an effective and efficient long reach system for material surface conditioning, surface treatment or removal of material from inside a member and, in particular, a system and method for forming a stator for a downhole motor and the internal structure of such a stator.